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Attic furnace
- Thread starter Chknman
- Start date
Jim greengo
Well-known member
80 or 90% what brand are you looking at?
Jim greengo
Well-known member
I'd say something in the 60,000 btu range,but differant brands have differant sizes to choose from.
Are you doing ac also?
Are you doing ac also?
Jim greengo
Well-known member
1.5-2t on the ac depending on how much you open the doors would be my suggestion.
The high ceilings push me more towards the 2t.
The high ceilings push me more towards the 2t.
larry4406
Well-known member
Gas furnace?
The high efficiency units can be challenging to install in attics. There is condensate to deal with to ensure it won't freeze. Also, in attics, vertical space is often limited forcing a horizontal installation. Horizontal installations can create challenges getting the condensate to drain properly if the unit is not level/internally pitched properly.
New construction guy and the company I work for did this in our homes (northern Va and MD). We had several service calls on the horizontal units due to condensate issues discussed above.
We did this for about 2-3 years till we changed the design of our homes to put the equipment fully inside the thermal envelope (nothing in the attic).
The high efficiency units can be challenging to install in attics. There is condensate to deal with to ensure it won't freeze. Also, in attics, vertical space is often limited forcing a horizontal installation. Horizontal installations can create challenges getting the condensate to drain properly if the unit is not level/internally pitched properly.
New construction guy and the company I work for did this in our homes (northern Va and MD). We had several service calls on the horizontal units due to condensate issues discussed above.
We did this for about 2-3 years till we changed the design of our homes to put the equipment fully inside the thermal envelope (nothing in the attic).
larry4406
Well-known member
Yes horizontal and will be gas. The furnace will be cost to the wall. Was thinking putting drain thru wall down to stone at base of garage. Do they still make a unit that doesn't have a condensate on the heat side I know I need one for the ac.
I think you need to stay low efficiency (~80%) to not generate condensate with the combustion but you then step up to metal B-vent flue. I’ve no experience with these in horizontal installation.
larry4406
Well-known member
I was planning a vertical vent.
Let me clarify:
..I’ve no experience with an 80% gas furnace (non-condensing) in a horizontal arrangement...
How cold a climate? ... putting a unit in an attic not in the conditioned space is like putting the unit outside. Most have 3-6r insulation ? think about it.
They use 80's in those spaces because higher efficiency units have water from the condensing process to worry about ... freezing.
Also - since ductwork leaks ... the placement tends to create negative pressure in the conditioned zone ... sucking in outside unconditioned air.
They use 80's in those spaces because higher efficiency units have water from the condensing process to worry about ... freezing.
Also - since ductwork leaks ... the placement tends to create negative pressure in the conditioned zone ... sucking in outside unconditioned air.